diff -r 944ec96bb103 -r 4d139ce8f7ec libpurple/protocols/yahoo/libymsg.c
--- a/libpurple/protocols/yahoo/libymsg.c	Sun Mar 10 23:31:01 2013 -0400
+++ b/libpurple/protocols/yahoo/libymsg.c	Sat Mar 16 14:02:10 2013 -0400
@@ -2536,7 +2536,7 @@
 	int pos = 0;
 	int pktlen;
 	struct yahoo_packet *pkt;
-	guchar *start = NULL;
+	guchar *start;
 	struct yahoo_p2p_data *p2p_data;
 	YahooData *yd;
 
@@ -2558,19 +2558,29 @@
 		return;
 	}
 
+	/* TODO: It looks like there's a bug here (and above) where an incorrect
+	 * assumtion is being made that the buffer will be added to when this
+	 * is next called, but that's not really the case! */
 	if(len < YAHOO_PACKET_HDRLEN)
 		return;
 
-	if(strncmp((char *)buf, "YMSG", MIN(4, len)) != 0) {
+	if(strncmp((char *)buf, "YMSG", 4) != 0) {
 		/* Not a YMSG packet */
+		purple_debug_warning("yahoo", "p2p: Got something other than YMSG packet\n");
+
+		start = (guchar *) g_strstr_len((char *) buf + 1, len - 1 ,"YMSG");
+		if (start == NULL) {
+			/* remove from p2p connection lists, also calls yahoo_p2p_disconnect_destroy_data */
+			if (g_hash_table_lookup(yd->peers, p2p_data->host_username))
+				g_hash_table_remove(yd->peers, p2p_data->host_username);
+			else
+				yahoo_p2p_disconnect_destroy_data(data);
+			return;
+		}
 		purple_debug_warning("yahoo","p2p: Got something other than YMSG packet\n");
 
-		start = memchr(buf + 1, 'Y', len - 1);
-		if (start == NULL)
-			return;
-
-		g_memmove(buf, start, len - (start - buf));
-		len -= start - buf;
+		len -= (start - buf);
+		g_memmove(buf, start, len);
 	}
 
 	pos += 4;	/* YMSG */
@@ -2578,7 +2588,17 @@
 	pos += 2;
 
 	pktlen = yahoo_get16(buf + pos); pos += 2;
-	purple_debug_misc("yahoo", "p2p: %d bytes to read\n", len);
+	if (len < (YAHOO_PACKET_HDRLEN + pktlen)) {
+		purple_debug_error("yahoo", "p2p: packet length(%d) > buffer length(%d)\n",
+				pktlen, (len - pos)); 
+		/* remove from p2p connection lists, also calls yahoo_p2p_disconnect_destroy_data */
+		if (g_hash_table_lookup(yd->peers, p2p_data->host_username))
+			g_hash_table_remove(yd->peers, p2p_data->host_username);
+		else
+			yahoo_p2p_disconnect_destroy_data(data);
+		return;
+	} else
+		purple_debug_misc("yahoo", "p2p: %d bytes to read\n", pktlen);
 
 	pkt = yahoo_packet_new(0, 0, 0);
 	pkt->service = yahoo_get16(buf + pos); pos += 2;